Charge movements and transverse tubular ultrastructure in organ cultured skeletal muscle

Abstract

A study was made of charge movements and the transverse tubular systems in rat EDL and soleus muscle fibres maintained for up to five days in organ culture. In the cultured EDL muscle the maximum amount of charge moved was about one third of that in innervated muscle. Charge movements in innervated soleus fibres are small, less than 10 nC/microF, and difficult to resolve. They remain small following organ culturing. The ultrastructural study examined the concentration of junctional feet because of their proposed key role in excitation-contraction coupling. The general architecture of the triads and the spacing of the feet in both muscle types was largely unchanged by culturing. In cultured EDL muscles the small changes in feet concentration did not parallel the large fall in charge movement. The results reported here support a previous conclusion that, in mammalian muscle, there is not a simple relation between charge and feet. The stimulation of cultured soleus muscles with a fast twitch pattern of electrical activity produced no observable changes in morphology.

Marked depletion of GLUT4 glucose transporters in transverse tubules of skeletal muscle from streptozotocin‐induced diabetic rats

“…Moreover, we have previously reported that insulin induces the translocation of GLUT4 to both the transverse tubules and the plasma membrane in rat skeletal muscle [9]. These studies, combined with the fact that transverse tubules constitute the largest (>60%) area of the cell surface in muscle cells [10,11], led us to propose that these tubular structures significantly contribute to the entry of glucose into myofi-*Corresponding author. Fax: (1) (418) 654 2247, bers, both in the basal and stimulated conditions.…”